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Appendix C: OpenDX: Industrial-StrengthData VisualizationMost of the visualizations we use in this book are 2-D, y(x) plots, or 3-D, z(x, y)(surface) plots. Some of the applications, especially the applets, use animations,which may also be 2-D or 3-D. Samples are found on the CD. We use and recommendGrace (2-D) and Gnuplot (2-D, 3-D) for stand-alone visualizations, and PtPlot forvisualizations callable from Java programs [L 05]. All have the power and flexibilityfor scientific work, as well as being free or open source.An industrial-strength tool for data visualization, which we also recommend, isOpenDX,orDX for short. 1 It was originally developed as IBM Data Explorer but hasnow joined the ranks of open-source software [DX1, DX2] and is roughly equivalentto the commercial package AVS. DX works under Linux, Unix, or a Linux emulator(Cygwin) on a PC. The design goals of DX were to• Run under many platforms with various data formats.• Be user-friendly via visual programming, a modern technique in which programsare written by connecting lines between graphical objects, as opposedto issuing textual commands (Figure C.3 right).• Handle large multidimensional data sets via volume rendering of f(x, y, z)as well as slicing and dicing of higher-dimensional data sets.• Create attractive graphics without expensive hardware.• Have a graphical user interface that avoids the necessity of learning manycommands.C DThe price to pay for all this power is the additional time spent learning how to donew things. Nevertheless, it is important for students of computational physics toget some experience with state-of-the-art visualization.This appendix is meant as an introduction to DX. We use it to visualize somecommonly encountered data such as scalar and vector fields and 3-D probabilitydensities. DX can do much more than that, and, indeed, is a standard tool in visualizationlaboratories around the world. However, the visualizations in this text arejust in gray, while DX uses color as a key element. Consequently, we recommendthat you examine the DX visualizations on the CD to appreciate their beauty andeffectiveness.Analogous to the philosophy behind the Unix operating system, DX is a toolboxcontaining tools that permit you to create visualizations customized to yourdata. These visualizations may be created by command-line programming (forexperienced users) or by visual programming. Typically, six separate steps are1 Juan Manuel Vanegas Moller and Guillermo Avendaño assisted in the preparation of thisappendix.−101COPYRIGHT 2008, PRINCET O N UNIVE R S I T Y P R E S SEVALUATION COPY ONLY. NOT FOR USE IN COURSES.ALLpup_06.04 — 2008/2/15 — Page 568